Voltage regulators are typically used in electronic circuits when it is desired to have a particularly stable input voltage for a particular electronic element or component. In particular, voltage regulators are typically used when it is desired to prevent a voltage input from rising above a particular level. A low-drop out, or LDO, regulator is a DC linear voltage regulator that can operate with a very small input/output differential voltage. The advantages of a low-drop out voltage include a lower minimum operating voltage, higher efficiency operation and lower heat dissipation. A traditional LDO regulator includes a transistor, typically a field effect transistor (FET) and a differential amplifier with a resistor divider in the feedback path. One input of the differential amplifier therefore monitors the fraction of the output determined by the resistor divider ratio, whilst the second input to the differential amplifier is from a stable voltage reference, such as a bandgap reference. If the output voltage rises too high relative to the reference voltage, then the drive to the transistor changes to maintain a constant output voltage.
However, the traditional LDO regulator structure using a resister divider as mentioned above, suffers from a number of drawbacks, particularly when implemented in integrated circuits. To limit the current drawn by the regulator then a large value of resister is needed in the feedback path. This large value resister requires a large silicon area on the integrated circuit. The large resister also creates an extra, undesired, pole in the feedback path, reduces the feedback factor and is a major contributor of noise in the system.